1. Field
Embodiments of the invention relate to aerial devices and utility platforms. More specifically, embodiments of the invention relate to the protection of insulated boom sections.
2. Related Art
Utility workers utilize an aerial device to reach inaccessible locations. The aerial device generally includes a boom assembly with a utility platform connected to a distal end of the boom. One or more utility workers stand in the utility platform. Utility workers typically use an aerial device to access overhead electric power lines and electric power components for installation, repair, or maintenance. The utility workers may also lift repair parts and other objects utilizing a jib associated with the utility platform. The utility platform and at least one boom section are highly insulated so as to prevent the discharge of electricity through the utility truck, and especially through the utility worker. Because at least one boom section is formed of fiberglass, or another polymer, structural strength of the boom is a consideration.
Four-bar linkages have been utilized in the prior art to determine the amount of load on the boom. However, four-bar linkages provide several drawbacks. First, four-bar linkages have friction that introduces an error into the strain calculations. Second, four-bar linkages often cause a hysteresis. Hysteresis is the tendency to make measurements not repeatable, because future results are affected at least in part by past results. For example, if you start with a first reading on the gauge, add a certain weight to obtain a second reading on the gauge, and then remove the weight to obtain a third reading on the gauge, then hysteresis is the first reading being different from the third reading, even though the weight on the boom is the same in both situations. Third, four-bar linkages of the prior art have a difficult time isolating the measurement of adverse loadings (i.e., other than in a straight-downward direction). Four-bar linkages measure a total or average loading thereon, this can be disadvantageous because the vertical loading is the most likely to cause a structural failure. Some four-bar linkages may isolate vertical loadings, but these are prone to hysteresis and error when manufactured within easily achievable tolerance and materials.